OH MASERS in THE MILKY WAY and BEYOND

There is a sense that field DIRECTIONS in the small, highly concentrated OH masers tend to mirror the LARGE-SCALE field directions in the local vicinity. OH masers are associated with HII regions, whose distances are known. Moreover, OH masers are BRIGHT. OH MASERS UNIQUELY OFFER LOCAL FIELD DIRECTIONS THROUGHOUT THE GALAXY

The Discovery of Extragalactic Magnetic Fields in OH Megamasers Tim Robishaw Carl Heiles Eliot Quataert Berkeley

Minimum energy and equipartition suggest magnetic fields in ULIRGs should be between 1 mG to 10 mG (Thompson et al. 2006) The Story

Minimum energy and equipartition suggest magnetic fields in ULIRGs should be between 1 mG to 10 mG (Thompson et al. 2006) ULIRGs (L FIR /L  >10 12 ) are powered by starbursts or AGN. The Story Arp 220  

Minimum energy and equipartition suggest magnetic fields in ULIRGs should be between 1 mG to 10 mG (Thompson et al. 2006) ULIRGs (L FIR /L  >10 12 ) are powered by starbursts or AGN. OH megamasers (L OH /L  = ) are found in ULIRGs (Darling & Giovanelli). The Story Arp 220  

Minimum energy and equipartition suggest magnetic fields in ULIRGs should be between 1 mG to 10 mG (Thompson et al. 2006) ULIRGs (L FIR /L  >10 12 ) are powered by starbursts or AGN. OH megamasers (L OH /L  = ) are found in ULIRGs (Darling & Giovanelli). In the Milky Way, OH masers probe magnetic fields in star formation regions. Went to Arecibo to observe the 6 brightest OHMs, including the archetypal ULIRG Arp 220, in hopes of measuring Zeeman splitting in the 1667 MHz line. The Story

Arp 220III Zw 35

Arp 220 Rovilos, Diamond, Lonsdale 2, & Smith "0.5" 1.5" = 550 pc

III Zw 35 Pihlström, Conway, Booth, Diamond, & Polatidis pc

Arp 220III Zw 35

Arp 220III Zw 35 +3mG-3mG

Gigamaser! L OH /L  >10 4 Pihlström, Baan, Darling, & Klöckner 2005 Yu pc

Gigamaser! L OH /L  >10 4

Gigamaser! Reversal18 mG! L OH /L  >10 4

Detected 15 B fields. Detected fields in 4/6 ULIRGs. First extragalactic Zeeman splitting detections in emission lines. –Only previous extragalactic Zeeman detection was HI in absorption in high-velocity cloud around Perseus A (Kazes et al. 1991; Sarma et al. 2005). B is similar to local sites of OH masers. –Conditions in regions of massive star formation are similar to those in Milky Way. B is consistent with inferred synchrotron fields. –Probing gas closer to typical Fascinating other issues: –B versus density –Linear polarization – thorny interpretive issues Results

More Data GBT survey of 7 ULIRGs awaiting reduction Arecibo survey continues this spring with the 6 next-brightest OHMs High-sensitivity VLBA observations of Arp 220 and III Zw 35

MAYBE YOU’VE NOTICED... (or maybe you don’t care...) All radio data in this talk used the just-pictured telescopes--Arecibo (the most sensitive in the world by a factor 3) and the VLBA (its angular resolution makes HST look sick)--which were recently bludgeoned to death by NSF’s SENIOR REVIEW COMMITEE ¡¡¡THANKS, GUYS!!!

SUMMARY Field affected by gas morphology—and vice-versa In CNM, morphology is primarily sheets/filaments. In CNM, P B  P turb  3 P thermal In CNM/WNM, field larger in “filaments” Galactic OH maser fields trace local large-scale field—only yesterday (Han/Zhang 2007) have we used this info! Extragalactic OH megamasers offer a unique probe into large-scale fields in ULIRGS.